Solar cell

ABSTRACT

A solar cell is discussed, which includes a pair of connecting electrodes having a portion having a width smaller than a width of a plurality of bus bar electrodes, and the pair of connecting electrodes connects a plurality of second finger electrodes to both sides of an end of one of the plurality of bus bar electrodes, respectively, wherein the end of the one of the plurality of bus bar electrodes being positioned in a second direction, wherein an area not including the plurality of second finger electrodes is positioned between the pair of connecting electrodes, and wherein an auxiliary electrode not connected to the plurality of second finger electrodes and having a width smaller than the width of the plurality of bus bar electrodes is disposed in the area not including the plurality of second finger electrodes.

CROSS-REFERENCE TO RELATED APPLICATION

This application is continuation of copending U.S. application Ser. No.13/312,028 filed on Dec. 6, 2011 which claims the benefit of KoreanPatent Application No. 10-2010-0123692 filed on Dec. 6, 2010 in theRepublic of Korea. The contents of all of these applications are herebyincorporated by reference as fully set forth herein in their entirety.

BACKGROUND

Field of the Invention

Embodiments of the invention relate to a solar cell, and moreparticularly, to a solar cell having an improved electrode structure.

Description of the Related Art

Recently, as conventional energy resource such as petroleum and coal areexpected to be exhausted and the environment is seriously polluted,significance of development in next-generation clean energy isincreasing. Also, demand for renewable energy is increasing in the 21stcentury, and thus, interest in solar cells is also increasing. Solarcells do not pollute the environment, use a practically infinite energyresource, and can be used semi-permanently. Thus, solar cells areexpected to be an energy source for solving future energy problems.

Solar cells can be largely classified into a crystalline silicon solarcell, a thin-film solar cell, and a dye-sensitized solar cell. The costof the crystalline silicon solar cell has increased due to a shortsupply of a silicon raw material and a shortage of a silicon substrateinduced by installing a large number of solar cell systems in recentyears. For this reason, a thin-film silicon solar cell, a dye-sensitizedsolar cell, and a plastic solar cell are in the spotlight because theircost is low, their consumption of the raw material is less, and theirsupply of the raw material is stable. Despite the low cost, however, lowconversion efficiency and short lifetime of the solar cells, such as thethin-film silicon solar cell, the dye-sensitized solar cell, and theplastic solar cell, are blocking the industrialization thereof.Therefore, recent studies about the solar cells are focused ontechniques for improving the efficiency of the solar cells. To improvethe efficiency of the solar cells, a structure or a pattern of a frontelectrode formed on a light incident surface of the solar cell needs tobe improved.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to a solar cellincluding a front electrode pattern that is able to minimize a loss of alight incident area.

A solar cell according to an embodiment of the invention includes aphotoelectric conversion layer and a front electrode on thephotoelectric conversion layer. The front electrode includes a bus barelectrode; at least one first finger electrode directly connected to thebus bar electrode; a plurality of connecting electrodes extending fromthe bus bar electrode and having a width smaller than a width of the busbar electrode, wherein the plurality of connecting electrodes includesportions that are spaced apart from each other to form a spacetherebetween; at least one second finger electrode connected to at leastone of the plurality of connecting electrodes; and an auxiliaryelectrode formed at the space between the portions of the plurality ofconnecting electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a solar cell according to anembodiment of the invention;

FIG. 2 is a schematic cross-sectional view of the solar cell shown inFIG. 1;

FIG. 3 is a plan view of a front electrode formed on a front portion ofa typical solar cell.

FIG. 4 is a partial view of a solar cell module formed by combining thesolar cells shown in FIG. 3;

FIG. 5 is a plan view of a front electrode formed on a front portion ofa solar cell according to an embodiment of the invention;

FIG. 6 is a partial view of a solar cell module formed by combiningsolar cells according to the embodiment of the invention; and

FIGS. 7 to 9 are plan views of finger electrodes and bus bar electrodesof the solar cell shown in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, it will be understood that when a layer orfilm is referred to as being “on” another layer or substrate, it can bedirectly on the other layer or substrate, or intervening layers may alsobe present. Further, it will be understood that when a layer is referredto as being “under” another layer, it can be directly under the otherlayer, and one or more intervening layers may also be present. In thefigures, the dimensions of layers and regions are exaggerated orschematically illustrated, or some layers are omitted for clarity ofillustration. In addition, the dimension of each part as drawn may notreflect an actual size.

Hereinafter, embodiments of the invention will be described withreference to the accompanying drawings.

FIG. 1 is an exploded perspective view of a solar cell according to anembodiment of the invention, and FIG. 2 is a schematic cross-sectionalview of the solar cell shown in FIG. 1.

Referring to FIGS. 1 and 2, a solar cell module 100 according to anembodiment of the invention includes a plurality of solar cells 150, aplurality of ribbons 143 for connecting the plurality of solar cells150, at least one bus ribbon 145 for connecting the ribbons 143, a firstsealing film 131 and a second sealing film 132 for sealing the solarcells 150 on both sides, a front substrate 110 for protecting a lightincident surface of the solar cells 150, and a rear substrate 120 forprotecting a rear surface of the solar cells 150.

Each solar cell 150 is a semiconductor device for converting solarenergy to electric energy. Referring to FIG. 2, the solar cell 150includes a photoelectric conversion layer 151, electrode layers 152formed on at least one surface of the photoelectric conversion layer151, and the ribbons 143 for connecting the solar cells 150. At aninterface surface of the electrode layer 152 and the ribbon 143, aeutectic mixture may be formed. In FIG. 2, the electrode layers 152include a front electrode layer and a rear electrode layer as anexample. However, embodiments of the invention are not limited thereto.Thus, the electrode layers 152 may be formed only at the rear surface ofthe photoelectric conversion layer 151 in other embodiments of theinvention. In this instance, the ribbon 143 connects the electrodelayers 152 formed on the rear surfaces (or the rear sides) of two solarcells 150 adjacent to each other among the solar cells 150.

The photoelectric conversion layer 151 may include silicon, a compoundsemiconductor, or a tandem structure. In the photoelectric conversionlayer 151, a P-N junction is formed, and thus, the electric energy isgenerated by a photoelectric effect when light, such as sun light, isincident.

The electrode layer 152 connected to a p-type layer 123 may be formed,for example, by coating a paste for an electrode including aluminum,silica, binder, and so on, on one surface on the photoelectricconversion layer 151 and heat-treating the paste. During a firingprocess, organic materials and a solvent included in the coated pasteare removed. Upon the heat-treating, the aluminum for forming theelectrode is diffused through the rear surface of the photoelectricconversion layer 151 to form a back surface field at the interface ofthe electrode layer 152 and the photoelectric conversion layer 151.

According to embodiments of the invention, the solar cell 150 includesthe ribbon 143, and the ribbon 143 is adjacent to (or attached to) onesurface of the electrode layer 152. At the interface of the electrodelayer 152 and the ribbon 143, the eutectic matrix may be formed. Atleast an outer surface of the ribbon 143 includes at least one of Cu,Nu, Ca, Sn, Zn, In, and Sb for a eutectic bonding.

A front surface of the photoelectric conversion layer 151 may include atextured surface. Performing texturing of the front surface forms apattern of convex-concave shapes or an uneven surface. Since the surfaceof photoelectric conversion layer 151 has a large roughness because ofthe textured surface, the reflectance of the incident light decreasesand the photoelectric conversion layer 122 absorbs more light. That is,the light loss can be reduced.

Referring again to FIG. 1, the ribbon 143 may include two lines attachedto an upper portion and a lower portion of the solar cells 150 in orderto connect the solar cells 150. The solar cells 150 electricallyconnected by the ribbon 143 form a string 140. A plurality of strings140 adjacent to each other may be arranged to form a plurality ofcolumns.

The bus ribbon 145 is positioned where the string 140 is not formed, andis connected to the ribbon 143. The bus ribbon 145 may be connected to alead line that is connected to a junction box for charging anddischarging the electric energy and for preventing countercurrent.

Also, the bus ribbon 145 alternately connects both ends of the ribbons143 of the strings 140, thereby electrically connecting the strings 140.The bus ribbon 145 may be arranged in a row direction at the both endsof the strings 140 arranged to form the plurality of columns. Thestrings 140 for forming the plurality of columns may be formed betweenthe first sealing film 131 and the second sealing film 132.

The first sealing film 131 may be positioned on the light incidentsurface of the solar cells 150, and the second sealing film 132 may bepositioned on the rear surface of the solar cells 150. The first sealingfilm 131 and the second sealing film 132 may be attached by a laminationmethod. The first sealing film 131 and the second sealing film 132 blockmoisture and oxygen that may be harmful to the solar cells 150.

In addition, the first sealing film 131 and the second sealing film 132chemically combine elements of the solar cells 150 to each other. Thefirst sealing film 131 and the second sealing film 132 may include anethylene-vinyl acetate (EVA) copolymer resin, polyvinyl butyral, anethylene-vinyl acetate having a partial oxide, a silicone resin, anester-based resin, and/or an olefin-based resin.

The front substrate 110 is positioned on the first sealing film 131 sothat the sun light can penetrate therethrough. The front substrate 110may be formed of a transparent material, such as a tempered glass, inorder to protect the solar cells 150 from an external impact.Specifically, the front substrate 110 may be a low-iron tempered glassin order to reduce or prevent the reflection of the sun light and toimprove the transmissivity of the sun light.

The rear substrate 120 protects the solar cells 150 at the rear surfacethereof and may be waterproof, may insulate, or may filter ultravioletlight. The rear substrate 150 may be a TPT (Tedlar/PET/Tedlar) type.However, embodiments of the invention are not limited thereto. Inaddition, the rear substrate 120 may include a material having a highreflectivity property in order to reuse the sun light incident throughthe front substrate 110, or include a material of a transparent propertythat allows the sun light to be incident.

FIG. 3 is a plan view of a front electrode formed on a front portion ofa typical solar cell, and FIG. 4 is a partial view of a solar cellmodule formed by combining the solar cells shown in FIG. 3. A solar cell200 shown in FIGS. 3 and 4 has a typical structure. The FIGS. 3 and 4show a front surface of the solar cell 200 where finger electrodes 220and bus bar electrodes 210 are formed.

FIG. 3 shows a typical pattern of the front electrode. FIG. 3 shows thepattern as including the finger electrodes 220 that are denselypositioned and the bus bar electrodes 210. However, such is just oneexample pattern of the front electrode. Thus, the front electrodeshaving various patterns are disclosed.

The front electrode having metal is formed on the front surface of thesolar cell 200 in order to collect charges generated by the incident sunlight. The front electrode includes grids that are generally referred toas the finger electrodes 220 or finger metal lines, and the bus barelectrodes 210 having a bar shape and being electrically connected tothe grids as main electrodes. When the solar cell 200 generates electricenergy, the electrons or the holes are collected by the bus barelectrodes 210 via the finger electrodes 220, and then, are collected bythe ribbon 145.

However, since the sun light is reflected by the front electrode, andthe sun light cannot penetrate the front electrode, the front electrodegenerates a shading loss and reduces the efficiency of the solar cell.Thus, in order to reduce the shading loss, an area of the frontelectrode that covers the light incident surface of the solar cell needsto be decreased. However, if the width of the finger electrodes isdecreased to reduce the contact area and the shading loss, resistance ofthe finger electrodes may be increased due to the reduction of thecross-sectional area of the electrodes. Thus, electric loss may beincreased.

That is, the front electrode on the front surface of the solar cells 200is needed to have an optimal structure for having a high opening ratioin order to absorb more light and for minimizing the resistance and theshading loss. Typically, the width and the area of the finger electrodes220 may be adjusted in order to improve the efficiency of the solarcells 200 by reducing the shading loss. However, the finger electrodes220 basically have a width larger than 100 μm, and thus, the adjustmentof the width and the area of the finger electrodes 220 is limited. Inaddition, a lithography method and a laser transfer method have beenproposed in order to reduce the width of the finger electrodes 220.However, the manufacturing cost of such methods may be high.

For example, the bus bar electrodes 210 of the solar cell 200 arepositioned to have a predetermined distance (about 2˜3 mm) from edges ofthe solar cell 200, and thus, the bus bar electrodes 210 have a lengthof about 153 mm in a solar cell 200 having a wafer size of 156 mm.Further, the ribbon 143 connecting the solar cells and being attachedthereto during manufacturing of a solar cell module have a predetermineddistance (C of FIG. 2; about 2 mm) from an end of the bus bar electrode210. Accordingly, the ribbon 143 is not attached to the solar cell at aportion 230 of the bus bar electrodes 210, and the portion 230 is a lossarea for reducing the light incident area.

FIG. 5 is a plan view of a front electrode formed on a front portion ofa solar cell according to an embodiment of the invention, and FIG. 6 isa partial view of a solar cell module formed by combining solar cellsaccording to the embodiment of the invention. The solar cell 300 shownin FIG. 5 according to an embodiment of the invention includes fingerelectrodes 320 and bus bar electrodes 310 having a structure differentfrom those of the solar cells 200 of FIG. 4. In the solar cell accordingto this embodiment of the invention, the bus bar electrodes 310 have ashape for reducing loss of the light incident area.

As shown in FIG. 5, the bus bar electrode 310 is shorter than a typicalbus bar electrode. That is, while the typical bus bar electrode isformed across essentially an entire light incident surface of the solarcell from one end (an upper end) to an opposite end (a lower end), anupper portion of the bus bar electrode 310 is formed differently (e.g.,not formed or partially removed) in the embodiment of the invention.Thus, the sun light can penetrate the upper portion of the bus barelectrode 310 where the ribbon is not connected. Accordingly, the lightincident area can increase, compared to a typical solar cell. Theimproved structure of the shapes of the bus bar electrodes 310 and thefinger electrodes 320 are shown in FIGS. 7 to 9.

FIGS. 7 to 9 are plan views of finger electrodes and bus bar electrodesof the solar cell shown in FIG. 5. That is, FIGS. 7 to 9 are enlargedviews of portions having shapes of the bus bar electrodes 310 and thefinger electrodes 320 of an improved structure. Referring to FIG. 7,finger electrodes 620 and 640 are connected to a bus bar electrode 610through connecting electrodes 630. The finger electrodes 620 and 640include first finger electrodes 620 and second finger electrodes 640.The first finger electrodes 620 are directly connected to the bus barelectrode 610, and the second finger electrodes 640 are connected to thebus bar electrode 610 through the connecting electrodes 630. Therefore,the second finger electrodes 640 have intersections 660 with theconnecting electrodes 630. The second finger electrodes 640 arepositioned at the upper portion of the solar cell, that is, at theportion where the part of the bus bar electrode 610 is not formed or isremoved.

Referring to FIG. 7, the bus bar electrode 610 and the connectingelectrodes 630 are vertically formed (or formed parallel to each other),and the first finger electrodes 620 and the second finger electrodes 640are horizontally formed (or formed parallel to each other). Thus, thebus bar electrode 610 and the first finger electrodes 620 intersect, andthe connecting electrodes 630 and the second finger electrodes 640 havethe intersections 660. The connecting electrodes 630 have a widthsmaller than that of the bus bar electrode 610, and thus, the area ofthe connecting electrodes 630 covering the light incident surface of thesolar cell is small. Thus, compared to the bus bar electrode 610, theconnecting electrodes 630 reduce the area generating the shading loss.The connecting electrodes 630 are formed at one end of the bus barelectrode 610 (specifically, the portion where the ribbon 143 is notattached to the bus bar electrode 610). Accordingly, the light incidentsurface can increase at the portion where the ribbon 143 is notattached.

Also, a portion of the second finger electrode 640 adjacent to theintersection 660 with the connecting electrode 630 may be bent (orinclined) at a predetermined angle. Thus, a path from the second fingerelectrode 640 to the connecting electrodes 630 can decrease.Accordingly, the shading loss can be reduced, and a metal paste used forforming the connecting electrodes 630 and the second finger electrodes640 can also decrease. In this instance, when the portion of the secondfinger electrode 640 has the angle of 45 degrees with the connectingelectrodes 630, the path from the second finger electrode 640 to theconnecting electrodes 630 can be minimized, compared with other angles.Considering a tolerance (or margin of error), the angle between thesecond finger electrode 640 and the connecting electrode 630 may be in arange of about 40 to about 50 degrees. Other angles may be used,including an angle of 90 degrees.

In addition, the width of the connecting electrode 630 may be changed atsome portions. The plurality of the second finger electrodes 640 (thatis, two or more second finger electrodes 640) are connected to oneconnecting electrode 630. Thus, when the connecting electrode 630 isuniform, the internal resistance of the connecting electrode 630increases as the number of the second finger electrodes 640 connected tothe connecting electrode 630 increase. The number of the intersections660 of the connecting electrode 630 with the second finger electrodes640 decreases as the distance from the bus bar electrode 610 increases.That is, in order to achieve uniform resistance, the connectingelectrode 630 may have a cross section gradually decreasing as thedistance from the bus bar electrode 610 increases. In this instance, theconnecting electrode 660 has the cross section varying at each of theintersections 660 of the connecting electrodes 630 and the second fingerelectrodes 640. In embodiments of the invention, a thickness of theconnecting electrodes 630 may increase based on the number ofconnections 660 made with the second finger electrodes 640 in going fromthe edge of the solar cell to the bus bar electrode 610.

However, embodiments of the invention are not limited thereto. Thus, ifsome amount of shading loss by the connecting electrodes 630 isacceptable, the connecting electrodes 630 may have a uniform crosssection though its entire length. In this instance, the connectingelectrodes 630 may have a cross section (which may be predetermined) ina range that the internal resistance of the connecting electrodes 630does not exceed a predetermined value.

In the embodiment of the invention, the plurality of the second fingerelectrodes 640 are connected to one connecting electrodes 630. Thus,when a short-circuit is generated at any one portion of the connectingelectrodes 630, the electrons-flowing path through the second fingerelectrodes 640 is blocked. Thus, in order to address the above instance,the plurality of the connecting electrodes 630 (that is, two or moreconnecting electrodes 630) may be formed. The plurality of connectingelectrodes 630 may be formed apart from each other to form a spacetherebetween. Thus, a space between the connecting electrodes 630 mayhave an opening 630 a, or may have a portion 630 b which is open towardan outside. At the space between the connecting electrodes 630, a bridgeelectrode 650 connecting the connecting electrodes 630 may be formed.Accordingly, when the short-circuit is generated at one connectingelectrode 630, the carriers flowing through the second finger electrodes640 connected to the one connecting electrodes 630 can flow toward thebus bar electrode 610 via the bridge electrode 650 and anotherconnecting electrode 630, so that ultimately, the second fingerelectrodes 640 connected to the connecting electrode 630 with theshort-circuit can be electrically connected to the bus bar electrode610. That is, the bridge electrode 650 is formed at the space disposedbetween the adjacent connecting electrodes 630 as an auxiliaryelectrode. Thus, the problem due to the short-circuit in the connectingelectrodes 630 can be addressed.

In this instance, the bridge electrode 650 may be connected to portionsof the connecting electrodes 630 that are positioned between twoadjacent second finger electrodes 640. Thereby, a problem due to aplurality of electrodes being concentrated at one portion can beaddressed. That is, the electrically connected portions can bedispersed, and thus, safety and stability can be improved. In theembodiment of the invention, the connecting electrodes 630 having widthssmaller than that of the bus bar electrode 610 are formed at one end ofthe bus bar electrode 610 where the ribbon 143 is not attached, andthus, an area of a light incident surface can increase at a portionwhere the ribbon 143 is not attached. Specifically, light can beincident through the opening 630 a defined by the bus bar electrode 610,the connecting electrodes 630, and the bridge electrode 650, or theportion 630 b open towards the outside between the connecting electrodes630, and thus, the area of the light incident surface can increase.

In embodiments of the invention, the bridge electrode 650 and theconnecting electrodes 630 may have a lattice arrangement. Also, when aplurality of bridge electrodes 650 are used, lengths of the plurality ofbridge electrodes 650 may be the same. Additionally, increase in thecross section of the connecting electrode 630 may produce steps thatface towards the outside (i.e., face towards the second fingerelectrodes 640).

FIG. 8 is a plan view of a front electrode according to anotherembodiment of the invention. As shown in FIG. 8, the front electrodeincludes a bus bar electrode 710, an auxiliary bus bar electrode 730,connecting electrodes 750, first finger electrodes 720, second fingerelectrodes 760, and a third finger electrode 740. In this instance, thefirst finger electrodes 720 are directly connected to the bus barelectrode 710 to have intersections therebetween. The auxiliary bus barelectrode 730 is extended from the bus bar electrode 710 and has a widthsmaller than the bus bar electrode 710. The third finger electrode 740is connected to the auxiliary bus bar electrode 730 and is nearer to anedge of the solar cell than the first and second finger electrodes 720and 760. The third finger electrode 740 is farthest from the bus barelectrode 710 as compared to the first and second finger electrodes 720and 760. Since the auxiliary bus bar electrode 730 is connected to thethird finger electrode 740 that are fewer in number than the first andsecond finger electrodes 720 and 760, the auxiliary bus bar electrode730 can have a width smaller than a width of the first bus bar 710. Inembodiments of the invention, the auxiliary bus bar electrode 730 mayextend parallel to the bus bar electrode 710, but may alternativelyextend non-parallel to the bus bar electrode 710. Also, a plurality ofauxiliary bus bar electrodes 730 may be connected to the bus barelectrode 710. The third finger electrode 740 may be connected to theauxiliary bus bar electrode 730 in a non-perpendicular manner in otherembodiments.

The embodiment of the invention includes the auxiliary bus bar electrode730 and the third finger electrodes 740 disposed at a space between theconnecting electrodes 750 as auxiliary electrodes. That is, a surfacearea available for light incidence can be sufficiently procured by thespace between the connecting electrodes 750, and the current generatedat the space between the connecting electrodes 750 can be collected bythe auxiliary bus bar electrode 730. The third finger electrodes 740connected to the bus bar electrode 730 allows the current generated atthe space between the connecting electrodes 750 to be collected evenmore. That is, in the embodiment of the invention, the current generatedat the portion between the connecting electrodes 750 can be effectivelycollected while surface available for light incidence can besufficiently procured at the portion where the ribbon 143 is notattached.

The auxiliary bus bar electrode 730 and the third finger electrodes 740may be disposed apart from the connecting electrodes 750 and the secondfinger electrodes 760 so that the current collected by the auxiliary busbar electrode 730 and the third finger electrodes 740 can flow to thebus bar electrode 710 through a shortest path.

In FIG. 8, a single third finger electrode 740 is shown as an example.However, embodiments of the invention are not limited thereto. Forexample, some finger electrodes that are disposed far away from the busbar electrode 710 may be the third finger electrodes 740. Also, in FIG.8, the third finger electrode 740 and the auxiliary bus bar electrode730 form a T shape. In another embodiment of the invention, the thirdfinger electrode 740 may be bent at an intersection with the auxiliarybus bar electrode 730, and thus, the third finger electrode 740 and theauxiliary bus electrode 730 may have a Y shape. In this instance, thepath from the third finger electrodes 740 to the auxiliary bus barelectrode 730 can be reduced even more. Also, the third finger electrode740 and the auxiliary bus electrode 730 may have a cross shape (+).

The second finger electrodes 760 have intersections with the connectingelectrodes 750, and are connected to the bus bar electrode 710 throughthe connecting electrodes 750. The connecting electrodes 750 include afirst region 751 having an intersection with the second fingerelectrodes 760 and a second region 753 connecting the second fingerelectrodes 760 and the bus bar electrode 710. The first region 751 ofthe connecting electrodes 750 is apart from the bus bar electrode 710,and the second region 753 is bent toward the bus bar electrode 710. Inthis instance, when the second region 753 has an angle of 45 degreeswith the first region 751 (as in the instance that a distance betweenone connecting electrode 750 and the bus bar electrode 710, and anotherdistance between another connecting electrode 750 and the bus barelectrode 710 are the same each other), the length of the connectingelectrodes 750 can be minimized Considering a tolerance (or a margin oferror), the angle between the second region 753 with the first region751 may be in a range of about 40 to about 50 degrees. Other angles maybe used.

The first region 751 of the connecting electrode 750 has intersections770 with the plurality of the second finger electrodes 760. The width ofthe first region 751 may increase as the number of the second fingerelectrodes 760 connected to the connecting electrodes 750 increases.That is, as the number of the intersections 770 with the second fingerelectrodes 760 accumulates, the cross section of the connectingelectrodes 750 increases, either gradually or in steps. Since the crosssection or the thickness of the connecting electrode 750 is adjusted asdiscussed above, the resistance by the connecting electrodes 750 can bemaintained below a predetermined value, regardless of the number of thesecond finger electrodes 760 connected to the connecting electrodes 750.That is, the first region 751 may have a cross section decreasing as adistance from the bus bar 710 increases. Although not required, thefirst region 751 of the connecting electrode 750 may be parallel to thebus bar electrode 710, while the second region 753 of the connectingelectrode 750 is non-parallel to the bus bar electrode 710.

In addition, the second finger electrodes 760 connected to theconnecting electrode 750 may be bent at a portion adjacent to theintersections 770 with the connecting electrodes 750 in order to shortenthe path formed by the second finger electrodes 760 to the connectingelectrodes 750. In this instance, in order to minimize the path, a bentangle may be about 40 to about 50 degrees (for example, 45 degrees), asdiscussed above.

FIG. 9 is a plan view of a front electrode according to still anotherembodiment of the invention. In the embodiment shown in FIG. 9, fingerelectrodes 830 are directly connected to connecting electrodes 820 or abus bar electrode 810. In this instance, two connecting electrodes 820are connected to one bus bar electrode 810. The connecting electrodes820 may be inclined with respect to the bus bar electrode 810 toward thefinger electrodes 830 in a range that lengths of the finger electrodes830 are not too short. Bent angles, the lengths, and widths of theconnecting electrodes 820 may be adjusted considering an amount of ametal paste that is used for forming the front electrode and theefficiency of the solar cell due to an area of the light incidentsurface.

Unlike the embodiment of the invention described in referring to FIGS. 7and FIG. 8, the finger electrodes 830 are not bent in the embodimentdescribed referring to FIG. 9. Thus, the finger electrodes 830(specifically, the finger electrodes 830 connected to the connectingelectrodes 820) may have a stripe shape. In this instance, because theconnecting electrodes 820 are inclined with respect to the bus barelectrode 810, and are bent toward the finger electrodes 830, the lengthof the finger electrodes 830 can decrease.

Instead of removing the end of the bus bar electrode 810, the connectingelectrodes 820 are connected to the finger electrodes 830. Thus, theshading loss due to the bus bar electrode 810 can be reduced orprevented, and the metal paste for forming the electrodes can bereduced. Also, considering a possibility of short-circuit at one of theconnecting electrodes 820, a bridge electrode 850 connecting both of theconnecting electrodes 820 may be included as an auxiliary electrode. Inaddition, the cross section of the connecting electrodes 820 maygradually decrease as the distance from the bus bar electrode 810increases, considering the number of the finger electrodes 830 that areconnected to the connecting electrodes 820 is smaller as the distancefrom the bus bar electrode 810 increases. The cross section of theconnecting electrodes 820 may be adjusted by controlling the width orthe thickness of the connecting electrodes 820.

In embodiments of the invention, the bridge electrode 850 and theconnecting electrodes 820 may have an A shape arrangement. Also, when aplurality of bridge electrodes 850 are used, lengths of the plurality ofbridge electrodes 850 may be different. Additionally, increase in thecross section of the connecting electrode 820 may produce steps thatface towards the outside (i.e., face towards the finger electrodes 830).

According to the embodiments of the invention, by improving a pattern ofa front electrode, the shading loss due to the front electrode formed onthe light incident surface of the solar cell can be reduced, and thus,the efficiency of the solar cell can be enhanced. Also, the materialcost for forming the front electrode can be also reduced.

Certain embodiments of the invention have been described. However, theinvention is not limited to the specific embodiments described above;various modifications of the embodiments are possible by those skilledin the art to which the invention belongs without departing from thescope of the invention defined by the appended claims. Also,modifications of the embodiments should not be understood individuallyfrom the technical principles or prospects of the invention.

What is claimed is:
 1. A solar cell comprising: a photoelectricconversion layer; and an electrode on the photoelectric conversionlayer, wherein the electrode comprises: a plurality of first fingerelectrodes extended in a first direction to be parallel to each other,wherein each of the plurality of first finger electrodes has a firstwidth; a plurality of second finger electrodes including portionsextended in the first direction to be parallel to each other, whereineach of the plurality of second finger electrodes has the first widthand the plurality of second finger electrodes are nearer to an edge ofthe solar cell than the first finger electrodes; a plurality of bus barelectrodes extended in a second direction crossing the first direction,wherein each of the plurality of bus bar electrodes has a second widthlarger than the first width and the plurality of bus bar electrodescross the plurality of first finger electrodes; and a pair of connectingelectrodes extended in a third direction different from the firstdirection, wherein each of the pair of connecting electrodes has aportion having a third width smaller than the second width, and the pairof connecting electrodes connects the plurality of second fingerelectrodes to both sides of an end of one of the plurality of bus barelectrodes, respectively, wherein the end of the one of the plurality ofbus bar electrodes being positioned in the second direction, wherein anarea not including the plurality of second finger electrodes ispositioned between the pair of connecting electrodes, and wherein anauxiliary electrode not connected to the plurality of second fingerelectrodes and having a fourth width smaller than the second width isdisposed in the area not including the plurality of second fingerelectrodes.
 2. The solar cell according to claim 1, wherein a width of aportion of at least one of the pair of connecting electrodes adjacent tothe one of the plurality of bus bar electrodes is larger than a width ofanother portion of the at least one of the pair of connecting electrodesadjacent to the edge of the solar cell.
 3. The solar cell according toclaim 1, wherein a width of at least one of the pair of connectingelectrodes increase toward the one of the plurality of bus barelectrodes.
 4. The solar cell according to claim 1, wherein at least oneof the pair of connecting electrodes has a cross section larger than across section of at least one of the plurality of first fingerelectrodes and the plurality of second finger electrodes.
 5. The solarcell according to claim 1, wherein the auxiliary electrode comprises abridge electrode connecting the pair of connecting electrodes.
 6. Thesolar cell according to claim 1, wherein at least one of the pluralityof second finger electrodes comprises a bent portion connected to atleast one of the pair of connecting electrodes and is inclined withrespect to the plurality of bus bar electrodes.
 7. The solar cellaccording to claim 1, wherein the auxiliary electrode comprises anauxiliary bus bar electrode extended in the second direction.
 8. Thesolar cell according to claim 1, wherein the auxiliary electrodecomprises an auxiliary finger electrode extended in a directiondifferent from the second direction.
 9. The solar cell according toclaim 1, wherein the auxiliary electrode comprises: an auxiliary bus barelectrode extended in the second direction; and an auxiliary fingerelectrode extended in a direction different from the second direction,and wherein the auxiliary bus bar electrode and the auxiliary fingerelectrode are connected to each other.
 10. The solar cell according toclaim 9, wherein the auxiliary finger electrode extends in the firstdirection, and wherein the auxiliary bus bar electrode and the auxiliaryfinger electrode form a T shape.
 11. The solar cell according to claim9, wherein the auxiliary finger electrode includes portions extending ina direction inclined to the second direction, and wherein the auxiliarybus bar electrode and the auxiliary finger electrode form a Y shape. 12.The solar cell according to claim 1, wherein at least one of the pair ofconnecting electrodes comprises a first region having an intersectionwith the plurality of second finger electrodes and a second region beingbent towards the one of the plurality of bus bar electrodes.
 13. Thesolar cell according to claim 12, wherein the first region has a crosssection that gradually decreases as a distance from the one of theplurality of bus bar electrodes increases.
 14. The solar cell accordingto claim 1, wherein at least one of the pair of connecting electrodes isinclined with respect to the plurality of bus bar electrodes.
 15. Thesolar cell according to claim 14, wherein the pair of connectingelectrodes and the one of the plurality of bus bar electrodes form a Yshape.
 16. The solar cell according to claim 14, wherein at least one ofthe pair of connecting electrodes has an angle of about 40 to about 50degrees with respect to the one of the plurality of bus bar electrodes.17. The solar cell according to claim 1, wherein the plurality of secondfinger electrodes have a stripe shape.
 18. The solar cell according toclaim 12, wherein the auxiliary electrode comprises a bridge electrodeconnecting the pair of connecting electrodes.
 19. The solar cellaccording to claim 1, wherein a space between the pair of connectingelectrodes has an opening, or has a portion which is open towards anoutside.
 20. A solar cell module comprising: a plurality of solar cells,each of the plurality of solar cells comprising a photoelectricconversion layer and an electrode on the photoelectric conversion layer;a connector for electrically connecting the electrodes of the pluralityof solar cells; a sealing film for sealing the solar cells; a frontsubstrate disposed on a front surface of the solar cell; and a rearsubstrate disposed on a rear surface of the solar cell, wherein theelectrode comprises: a plurality of first finger electrodes extended ina first direction to be parallel to each other, wherein each of theplurality of first finger electrodes has a first width; a plurality ofsecond finger electrodes including portions extended in the firstdirection to be parallel to each other, wherein each of the plurality ofsecond finger electrodes has the first width and the plurality of secondfinger electrodes are nearer to an edge of the solar cell than the firstfinger electrodes; a plurality of bus bar electrodes extended in asecond direction crossing the first direction, wherein each of theplurality of bus bar electrodes has a second width larger than the firstwidth and the plurality of bus bar electrodes cross the plurality offirst finger electrodes; and a pair of connecting electrodes extended ina third direction different from the first direction, wherein each ofthe pair of connecting electrodes has a portion having a third widthsmaller than the second width, and the pair of connects electrodesconnecting the plurality of second finger electrodes to both sides of anend of one of the plurality of bus bar electrodes, respectively, whereinthe end of the one of the plurality of bus bar electrodes beingpositioned in the second direction, wherein the connector electricallyconnects the bus bar electrodes of the plurality of solar cells, whereinan area not including the plurality of second finger electrodes ispositioned between the pair of connecting electrodes, wherein anauxiliary electrode not connected to the plurality of second fingerelectrodes and having a fourth width smaller than the second width isdisposed in the area not including the plurality of second fingerelectrodes, and wherein an end of the connector is positioned in thearea not including the plurality of second finger electrodes.